Doctrine holds that since the disciples were all male, only men should be involved; previous pontiffs have performed the rite in the sanctity of Rome's basilicas, bathing the feet of chosen (male) priests.

Then again, writes Father Dwight Longenecker, Jesus himself "repeatedly flouted some strict rules for a greater good." Francis may have taken a radical step, but he reminds us of "the unexpected and sometimes upsetting example of the Lord himself – who upset some religious traditions in order to make a point."

The Vatican's spokesman, meanwhile, sought to downplay the gesture's implications.

"Excluding the girls would have been inopportune in light of the simple aim of communicating a message of love to all, in a group that certainly didn't include experts on liturgical rules," Rev. Federico Lombardi told the AP.

The impassioned debate it has provoked, however, suggests that the Pope's act has already resonated far beyond that group.